It has long been typical on gasoline dispensing sites to essentially utilize separate systems for dispensing different grades of leaded gasoline such as "premium," and "regular." On-site dispensers for like grades are hydraulically coupled with each individual dispenser frequently having its entirely own meter, computer, etc. separate from the others. With the advent of blending-type dispenser pumps, an increasing number of intermediate fuel grades became available from a single pump dispenser by blending various mixtures of regular and premium prior to entering the dispenser nozzle. Blending pumps as, for example, disclosed in U.S. Pat. Nos. 3,838,797 and 3,424,348 established a trend away from using separate dispenser units by making a variety of fuel grades available from a common dispenser operating a single computer. However, with the introduction of unleaded fuels for model cars beginning with 1975, the trend was essentially reversed by the requirement to maintain complete and total isolation between the unleaded and leaded dispensing systems. Needless to say, these completely separate systems have proven costly for the station proprietor but despite recognition of the problem, a ready solution has not heretofore been known.